The purpose of this study is to determine whether nifedipine, a calcium channel blocking drug, has beneficial therapeutic effects in patients with hypertrophic cardiomyopathy and, if so, how these effects compare with those of another calcium channel blocker, verapamil, which we have shown improves exercise capacity and subjective symptomatology in these patients. It is possible that the weaker nifedipine effect may have been due to a dosing schedule which did not maintain adequate nifedipine levels through a 24 period.